The overall objective of this project is to investigate various aspects of the antitumor activity of C. parvum against syngeneic murine tumors and to study the mechanism(s) by which this bacterium exerts an antitumor activity. The tumors that will be studied include: a methylcholanthrene-induced fibrosarcoma, and two spontaneously arisen mammary carcinomas, in C3Hf/Bu specific-pathogen-free mice. Most studies will deal with therapy; C. parvum will be injected at different intervals after sc or iv transplantation of tumor cells. Also, the therapeutic effect of this bacterium will be determined against spontaneous pulmonary metastases of a mammary carcinoma. Further, studies involving the combination of this therapy with radiotherapy and chemotherapy will be carried out. In resolving the mechanism(s) by which C. parvum induces antitumor activity, in vitro and in vivo studies on the destructive effect of peritoneal macrophages, spleen and lymph node cells (separated into T and B lymphocytes) against tumor cells will be carried out. C. parvum is an anaerobic corynebacterium which in nonviable form exerts strong antitumor adjuvant activity against many tumors so far studied in experimental animals. This property of anaerobic corynebacteria might be valuable in immunotherapy of malignant tumors in man.